A semiconductor light-emitting diode (LED) includes a substrate; a light emitting region; and a pair of electrodes for powering the diode. The substrate may be opaque or transparent. Light emitting diodes which are based on gallium nitride compounds generally include a transparent, insulating substrate, i.e., a sapphire substrate. With a transparent substrate, light may be utilized from either the substrate or from the opposite end of the LED which is termed the xe2x80x9cwindowxe2x80x9d.
The magnitude of the light emitted by an LED depends on: (a) the percent of the light emitting region that is activated by current flowing between the electrodes; (b) the efficiency of the window structure; and (c) the internal losses of generated light.
If the light that exits through the window is being utilized, some of the light directed to and through the transparent substrate is lost. Similarly, if the light that exits through the substrate is being utilized, some of the light directed to and through the window is lost.
An LED having a transparent substrate which is consistent with the present invention, includes an external optical reflector formed directly on the face of the LED which is not being used to exit useful light. If light from the window is being utilized, a reflector is formed directly on the xe2x80x9cbacksidexe2x80x9d of the substrate. However, if light through the substrate is being utilized, a reflector is formed directly on the light-emitting portion of the window.
In accordance with this invention, a Distributed Bragg Reflector (DBR) may be formed on either the backside of the substrate or on the window. Advantageously the light emitted is increased by 50 to 100 percent.